In LINQ to XML programming, you should not manipulate or modify a set of nodes while you are querying for nodes in that set. In practical terms, this means that you should not iterate over a set of nodes and remove them. Instead, you should materialize them into a List<T> by using the ToList<TSource> extension method. Then, you can iterate over the list to remove the nodes. For more information, see Mixed Declarative Code/Imperative Code Bugs (C#) (LINQ to XML).

Alternatively, if you want to remove a set of nodes, it is recommended that you use the Extensions::Remove method. This method copies the nodes to a list, and then iterates over the list to remove the nodes.

The XContainer stores its child nodes as a singly-linked list of XNode objects. This means that the Remove method must traverse the list of direct child nodes under the parent container. Therefore, using this method might affect your performance.